Heredity Prenatal Development and Birth Chapter 2 Mechanism
Heredity, Prenatal Development and Birth Chapter 2
Mechanism of Heredity z. Egg & sperm each have 23 chromosomes y. Contain genetic material (DNA) y. Combine at conception into 23 pairs x 23 rd pair determines sex (XX XY)
Mechanism of Heredity z. DNA consists of chemical compounds organized into strings wrapped together y. Adenine, thymine, guanine, cytosine y. Order is unique for each individual x. Cause cells to produce specific amino acids, proteins & enzymes (building blocks) x. A group of compounds providing set of biochemical instructions = a gene (genotype) - 30, 000 genes x. Genes are functional unit of heredity & are the basis for all human characteristics (phenotype)
Mechanism of Heredity z. Genes come in different forms called alleles y 2 alleles can be the same or different y. Homozygous or heterozygous x. Same: alleles produce the phenotype x. Different: dominant allele produces phenotype z. Some characteristics are caused by 1 gene y. Blood type, vision, hearing, eye color x. However some (psychological, behavioral) are rarely due to a single gene
Behavioral Genetics z. Study of inheritance of psychological and behavioral characteristics y. Not either or features (continuous range) y. Most polygenic (multiple gene inheritance) x. For example: perhaps 100 genes code for extraversion (producing a range from low to high) x. Difficult to determine specific genes involved x. Can determine amount of population variance due to genes (heritability)
Behavioral Genetics z. Research Methods y. Twin studies (MZ DZ) x. MZ > DZ implicates genes y. Adoption studies x. Greater similarity among biological than adopted relatives implicates genes > environment y. Molecular genetics x. Identify specific segments/alleles on genes x. Determine which contribute to some characteristic
Heredity & Environment z. Genotypes are set at conception y. Phenotypes determined by genes & environment z. Genes determine likelihood of behavior y. Which also depends on the environment x. Musical genotype + athletic environment reduces (p) of musical behavior y. Reaction range: phenotype range limited by genotype x. Ultimate position determined by environment
Heredity & Environment z 3 forms of interaction y 1. Passive: parental genotype passes to child along with early rearing environment y 2. Evocative: children’s genotypes evoke different reactions from environment y 3. Active: people seek experiences conforming to their genotype
Nature of Nurture z. Genes make us similar z. Non-shared environmental influences make us different y. Shared environmental influences only weakly influence development x. Siblings not much alike y. Unique environmental experiences that are key x. Siblings experience in same family very different
Influences on Prenatal Development z. Nutrition y. Caloric intake increased by 10%-20% x 25 -35 lbs gained (fetus, placenta, fat stores) x. Proteins, vitamins minerals key • Folic acid key for nervous system (spina bifida) y. Poor nutrition can lead to early, underweight birth x. Increase risk for various developmental problems
Influences on Prenatal Development z. Stress y. Primates: leads to small offspring prone to various problems y. Humans: associated w/ premature, small birth x. Stress hormones reduce flow of O 2 to fetus x. Stress weakens immune system x. Increases tendency to smoke, poor eating or exercise • Prolonged, extreme stress
Influences on Prenatal Development z. Mother’s age y. Teens, > 35 more problems (20 -35 best) y 20 s 2 x as fertile as women in 30 s x> 35 risk for miscarriage increases x 40 -45 ~50% pregnancies end in miscarriage
Influences on Prenatal Development z. Teratogens: agent causing abnormal PD z. Drugs y. Nicotine: constricts blood vessels and reduces O 2 & nutrients to fetus x. Miscarriage, small birth weight, impaired attentional, language and cognitive skills, behavioral problems y. Alcohol: Fetal Alcohol Syndrome x. Physical abnormalities, leading cause of mental retardation in US, other problems common
Influences on Prenatal Development z. Diseases y. Colds, flu no impact y. Bacterial, viral infections can cause problems z. Environmental Hazards y. Lead, mercury, PCBs (even tiny amounts)
Teratogens: How z Impact depends on genotype y. Not all species equally impacted z Exposure timing critical y. Zygote: spontaneous abortion y. Embryo: major defects in bodily structure y. Fetus: body system lamfunction z Effects specific to the teratogen y. Different body systems for different Teratogens
Teratogens: How z. Dosage key z. Damage may emerge later in life
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